M00.80

Bacterial joint infection caused by organisms other than staphylococci, pneumococci, streptococci, or gram-negative bacteria, with the specific joint not documented or not determinable.

Verified May 8, 2026 · 5 sources ↓

Status: Billable
Chapter: 13
Related CPT: 11
Region: General

Drawn from CDCICD10DataAAPCCMS

Documentation tips

What should appear in the chart to support M00.80.

Source · Editorial brief grounded in 5 cited references ↓

Identify the causative organism by name in the note and add the corresponding B96 code — this is a mandatory tabular instruction, not optional.
Document the specific joint by name (e.g., left knee, right wrist); if the joint is known, use a site-specific M00.8x code instead of M00.80.
Record all diagnostic workup supporting infectious etiology: joint aspiration results, synovial fluid WBC and differential, Gram stain, culture and sensitivity, ESR, CRP, and blood cultures.
Document whether a prosthetic joint is involved — if so, M00.80 is excluded and T84.5- applies.
Note comorbidities (immunosuppression, diabetes, IV drug use, recent joint injection or surgery) that support medical necessity and affect DRG CC/MCC assignment.
If the infection affects multiple joints, use M00.80 only for the unspecified site; code each identified joint separately with the site-specific M00.8x subcodes.

Related CPT procedures

Procedure codes commonly billed with M00.80. Linking the right diagnosis to the right procedure is what establishes medical necessity.

Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis

20600 $56.11

Needle aspiration and/or injection of a small joint or bursa — such as a finger or toe joint — performed without ultrasound guidance.

20604 $87.18

Arthrocentesis, aspiration and/or injection of a small joint or bursa (e.g., fingers, toes) performed with ultrasound guidance, including permanent image recording and reporting.

20605 $57.12

Aspiration and/or injection of an intermediate joint or bursa — such as the wrist, elbow, ankle, acromioclavicular joint, or olecranon bursa — performed without ultrasound guidance.

20606 $94.19

Aspiration and/or injection of an intermediate joint or bursa — such as the wrist, elbow, ankle, acromioclavicular, temporomandibular, or olecranon bursa — performed with real-time ultrasound guidance and permanent image recording and reporting.

20610 $68.81

Aspiration and/or injection of a major joint or bursa (shoulder, hip, knee, or subacromial bursa) performed without ultrasound guidance.

20611 $104.21

Aspiration or injection of a major joint or bursa performed under real-time ultrasound guidance, with permanent image documentation.

27310 $689.06

Open arthrotomy of the knee for exploration, drainage of infection, or removal of a foreign body or loose material from the joint space.

27331 $459.60

Open arthrotomy of the knee joint for exploration, biopsy, or removal of loose or foreign bodies.

29800 $508.70

Diagnostic arthroscopy of the temporomandibular joint (TMJ), with or without synovial biopsy, performed as a separate procedure.

29830 $439.22

Diagnostic arthroscopy of the elbow joint with or without synovial biopsy, performed for evaluation of intra-articular pathology.

29860 $615.24

Diagnostic arthroscopy of the hip joint, with or without synovial tissue biopsy, performed as a separate procedure.

Common coding pitfalls

The recurring mistakes coders make with M00.80 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

Omitting the B96 category code to identify the bacterium — the tabular 'Use Additional Code' instruction at M00.8 makes this mandatory, and skipping it is an audit vulnerability.
Using M00.80 when the joint is documented: if the note names the affected joint, the site-specific M00.8x subcode is required; M00.80 is not a valid shortcut.
Applying M00.80 to a prosthetic joint infection — that scenario is a Type 2 Excludes and must be coded to T84.5-, not M00.80.
Confusing M00.80 with septic arthritis from staphylococci (M00.0x) or streptococci (M00.2x); organism identity drives subcode selection across the entire M00 category.
Failing to capture CC/MCC comorbidities that affect DRG assignment to 548 vs. 549 vs. 550 — septic arthritis DRG weight drops significantly without accurate complication coding.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

M00.80 is the catch-all billable code within the M00.8 family for pyogenic (septic) arthritis caused by bacteria that don't fall under the more narrowly defined subcategories — specifically excluding staphylococcal (M00.0x), pneumococcal (M00.1x), streptococcal (M00.2x), and other gram-negative (M00.2x) pyogenic arthritis. The 'unspecified joint' designation makes this the lowest-specificity option in the M00.8x series; use it only when the affected joint is genuinely not documented, not when the coder simply hasn't confirmed it. If the joint is known, select the site-specific code (e.g., M00.811 for right shoulder, M00.861 for right knee).

The parent code M00.8 carries a mandatory 'Use Additional Code' instruction: always pair M00.80 with a code from category B96 to identify the causative organism. Failure to add the B96 code violates ICD-10-CM tabular instructions and can trigger a compliance flag. This code maps to MS-DRGs 548–550 (Septic Arthritis with MCC / with CC / without CC/MCC), so accurate complication and comorbidity coding directly affects DRG weight and reimbursement.

Note the Type 2 Excludes at the M00 category level: infection and inflammatory reaction due to an internal joint prosthesis routes to T84.5-, not M00.80. If a prosthetic joint is involved, T84.5- is the correct code regardless of the organism.

Sibling codes

Other billable codes under M00.8 (laterality / anatomic variants).

M00.89

Polyarthritis due to other bacteria

M00.88

Arthritis due to other bacteria, vertebrae

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 5 cited references ↓

01When is M00.80 appropriate versus a more specific M00.8x code?

Use M00.80 only when the affected joint is genuinely not documented or determinable. If the note identifies the joint — even informally — use the corresponding site-specific subcode. M00.80 is not an acceptable shortcut when joint location is available.

02Do I always need a B96 code alongside M00.80?

Yes. The tabular 'Use Additional Code' instruction at parent M00.8 requires a B96 category code to identify the causative organism whenever it is known. Even if culture results are pending at the time of coding, add B96 when results become available and an amended claim or encounter reflects that data.

03Can M00.80 be used for a periprosthetic joint infection?

No. A Type 2 Excludes note at the M00 category level explicitly excludes infection and inflammatory reaction due to an internal joint prosthesis; those cases route to T84.5-. Using M00.80 for a prosthetic joint infection is a coding error.

04Which MS-DRGs does M00.80 map to?

M00.80 groups to MS-DRG 548 (Septic Arthritis with MCC), 549 (with CC), or 550 (without CC/MCC) under MS-DRG v43.0. Accurate CC and MCC comorbidity coding is critical because the reimbursement difference between DRG tiers is substantial.

05What if multiple joints are infected by the same non-specific bacterium?

Code each identified joint separately using the appropriate site-specific M00.8x subcode. If one joint remains unspecified after thorough documentation review, M00.80 can cover that site. Do not use M00.80 as a single catch-all when multiple specific joints are documented.

06How does M00.80 differ from M00.80 when staphylococcus is the identified organism?

Staphylococcal pyogenic arthritis has its own subcategory: M00.0x. If the culture or clinical impression identifies staphylococcus, M00.0x (with appropriate site character) is correct — not M00.80. M00.8x is reserved for organisms outside the specifically named categories in M00.0–M00.2.

07Is a joint aspiration required for this diagnosis to be billable?

ICD-10-CM does not mandate a specific diagnostic procedure for billability — M00.80 is a billable code. However, payers assessing medical necessity will expect documentation of clinical signs of joint infection and supporting lab or imaging findings. An aspiration with synovial fluid analysis is the standard of care and the strongest audit defense.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

01CDC ICD-10-CM Tabular List 2026 (effective Oct 1, 2025)
02
icd10data.com
https://www.icd10data.com/ICD10CM/Codes/M00-M99/M00-M02/M00-/M00.80
03
aapc.com
https://www.aapc.com/codes/icd-10-codes/M00.80
04
cms.gov
https://www.cms.gov/Medicare/Coding/ICD10/Downloads/2019-ICD10-Coding-Guidelines-.pdf
05
cms.gov
https://www.cms.gov/medicare/coding/icd10/downloads/icd10clinicalconceptsorthopedics1.pdf

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